Posted
by
Soulskill
on Friday December 20, 2013 @01:32PM
from the new-television-series-already-under-development dept.

An anonymous reader sends word that 'Bertha,' the world's largest tunneling machine, which is currently boring a passage beneath Seattle's waterfront, has been forced stop. The 57.5ft diameter machine has encountered an unknown obstruction known as "the object.""The object’s composition and provenance remain unknown almost two weeks after first contact because in a state-of-the-art tunneling machine, as it turns out, you can’t exactly poke your head out the window and look. 'What we’re focusing on now is creating conditions that will allow us to enter the chamber behind the cutter head and see what the situation is,' [said project manager Chris Dixon]. Mr. Dixon said he felt pretty confident that the blockage will turn out to be nothing more or less romantic than a giant boulder, perhaps left over from the Ice Age glaciers that scoured and crushed this corner of the continent 17,000 years ago. But the unknown is a tantalizing subject. Some residents said they believe, or want to believe, that a piece of old Seattle, buried in the pell-mell rush of city-building in the 1800s, when a mucky waterfront wetland was filled in to make room for commerce, could be Bertha’s big trouble. That theory is bolstered by the fact that the blocked tunnel section is also in the shallowest portion of the route, with the top of the machine only around 45 feet below street grade."

How do we know that the SCP Foundation wasn't already aware of this object, and the whole tunneling project wasn't actually a cover for securing it? Rest assured that whatever "it" is, "they" have a suitably mundane explanation already prepared.

Yeah, pretty much. But in this case, I will put my money on the hull of a schooner. Old piece of garbage got dumped there wholesale I'll wage.

150 years ago:Person A: "Hey, we need landfill. Do you want this leaky decrepit hulk any more?"Person B "Give me 20 bucks and it's yours."Person A: "Here you go, thanks! That'll make great landfill and as long as anyone doesn't try to dig a giant tunnel through here, we're set!

They couldn't build an Earth tunneling machine that cant deal with a giant boulder ?

The cutter heads break apart stationary rock and other objects. The theory in the local press here in Seattle is that the bolder is being spun with the cutter head, thus the cutter teeth canâ(TM)t grip it, and itâ(TM)s too big to fall through the openings in the cutter head that channel debris to the exit conveyor.

I'm betting on a lost anchor or random pieces of cast iron from an old ship.

The problem is that while current grade level is forty five feet above the machine, historical grade is twenty feet above the machine... Who'd dig a thirty or forty foot deep hole in a swamp to discard an anchor or piece of cast iron? While this is the lowest point of the tunnel, this isn't the lowest point of the historical grade (relative to the tunnel bore), that's a block or two ahead of where the machine is currently stopped.

Clearly The Object is an interstellar vehicle with a structure of super-dense composite materials built to withstand the vagaries of near-light-speed travel for thousands of years. It crashed here long before human tribes crossed the land bridge from siberia and has remained undiscovered until now. They are best off leaving it undisturbed, if they enter it, they risk releasing biomechanoid killing machines that will destroy all of humanity.

Clearly The Object is an interstellar vehicle with a structure of super-dense composite materials built to withstand the vagaries of near-light-speed travel for thousands of years. It crashed here long before human tribes crossed the land bridge from siberia and has remained undiscovered until now. They are best off leaving it undisturbed, if they enter it, they risk releasing biomechanoid killing machines that will destroy all of humanity.

Yes, but thousands of years? Try billions. The pilot was killed on impact and eaten by their own gut microbes, which quickly escaped and went looking for more things to eat. Failing to find a single suitable eatery, the microbes went on to destroy most existing anaerobic life [wikipedia.org], become sentient, create eateries, and re-discover their long lost progenitor's ship thus activating its homing beacon through very efficient electromagnetic induction. Unfortunately, Earth's inhabitants could no longer serve the role as gut microbes due to a gross miss calculation in scale, and were instead eaten by a transdimensional dog named Jeebus after fetching them. Within said belly they reside to this day battling his mentally corrosive digestive juice which is rich in charged retardation and litigation particles known locally therein as: Religions.

This has all happened before, and will all happen again; The process has been deemed "mostly harmless".

This tunnel was locally controversial, with opponents arguing that- it was expensive- it wouldn't help with Seattle's traffic problems, AND- these monster boring machines have a track record of getting stuck underground, and then what are you going to do? Call Roto-Rooter?

I'm no engineer but I'm guessing the machine was never meant to bore through solid rock like that. The procedure for rock is still drill-and-blast.

Actually; it CAN break up solid rock. The current guess is that the rock isn't staying stationary, but is instead spinning, preventing the drill from gaining purchase. By the time they're done, maybe it'll be a perfect cylinder:)

It's hard to imagine a "piece of old Seattle" that would interfere with a tunneling machine. I'm guessing they're right, and it's an erratic from the ice age. I'd love to get to go in the tunnel and look, though - the tunneling equipment Seattle's been using both for this one and for the light rail extension fascinates me.

Upon further investigation they've determined the object has a hatch. The plan to spend the next couple of seasons trying top open it.
They're not not the only ones in the tunnel...and they all know it!

... having a 57.5ft tunnel with only 45ft of material above it. Aren't they worried about a cave-in? Unless they're plowing through heavily clay-laden (damned near bunker-buster-proof) soil like we have around where I live, surely the vibrations will have an effect on that 45ft of soil overhead if they decide to proceed and Bertha begins grinding its way through The Object.

Actually they did think of that. It's replacing a double-decker viaduct highway along the shoreline. One which was found to have weaknesses that make it not where you would want to be during an earthquake. You're also a lot more likely to be drowned in an open-air highway viaduct along the shore than in an underground tunnel. It's that little matter of the wave going horizontally, and not down through yards thick of earth.

They are concerned and not just about a cave-in. Vibration could cause lot's of damage. According to the WSDOT the machine is not actually stuck yet. They stopped it because they encountered resistance. The walls behind the machine are already built so there's not much risk of a cave-in. But there is a risk that nearby infrastructure could be damaged if they move forward. They can reinforce the infrastructure above but if they actually get stuck it could have enormous consequences. The machine would have to be dug out and replaced (at $80 million per borer). Add in the cost of reinforcements and digging a big hole, then consider that the $3.1 billion project is only bonded up to $500 million.

Here is a nice video from a company [youtube.com] that makes these rather impressive machines it should answer all of your question as to how they work and why they don't have cave ins behind the machine. In softer than expected soil, like hitting a deep spot of dirt in limestone, sink holes can develop in front of the cutting head as was a frequent problem on the SMART Tunnel [wikipedia.org] in Kuala Lumpur, Malaysia.

I am not a tunnel excavating expert but my 5 year old thinks these are among the coolest machines that have ever been constructed and likes educational shows that are about tunneling where they use a TBM.

If they check history carefully, they will find that in prehistoric times the people living there wanted a tunnel and began to bore it from the other end before money ran out. Bertha is just running into the front end of Big Bertha and they are butting (spinning) heads.

The good news is that the tunnel will now be completed ahead of schedule and we will also learn more about the irresistible force paradox [wikipedia.org].

It seems pretty strange that there's no provision for looking in front of the machine. You'd almost expect that there would be some kind of camera or way to poke a camera out an opening to see what's in front of them.

I would assume than running into weird shit digging a tunnel would be typical, although maybe it's designed with so much boring power that they only really expect to look at the overburden on the conveyor behind the boring machine.

Putting a camera or hatch on the front of the cutting head makes no sense. It presses hard against a rock face and would just get smashed or scuffed up. A number of these machines will have some forward looking capacity by taking a core sample ahead of the machine regularly but unless the sample managed to drill into the unknown object they wouldn't know it was there.

This is an earth-pressure-balance type TBM built for soft sand and dirt, below water level. Compressed air is used to keep water out at the working face. That's what's needed for a tunnel under the Seattle waterfront. It can cope with rocks and boulders, but not a solid rock face. It's not a hard-rock TBM. Those have very different cutters, but can't handle waterlogged soil.

It's the subterranean alien control station through which, via the extreme illuminati, the governments of the US are controlled. The tinfoil hat brigade have been warning us for years, and now we have irrefutable evidence.

No can do. As the machine moves forward the tunnel walls are built behind it. TBM's have no reverse.

Actually the machine isn't stuck, yet. They stopped the machine because it encountered resistance. If it actually does get stuck the machine can't be dismantled underground and removed. They would have to dig it out from above, remove the TBM and install a new one. If it does get stuck let's just hope it's not under a skyscraper.